In 2012, documentary filmmaker AJ Schnack (“Kurt Cobain About a Son”) took his camera in hand and followed a singularly wacky field of Republican presidential candidates around Iowa, where they tirelessly pressed sunburned Midwestern flesh, ate corn dogs, speechified on top of hay bales and otherwise worked the 99-county room that, in community halls, homes and schools several months later, would decide their political fates.

With the election long since passed, the GOP primary campaigners seem even goofier and more surreal than they did at the time, when Tim Pawlenty (remember him?) earned the distinction of the first drop-out and Texas governor Rick Perry actually looked like a possible frontrunner until Michele Bachmann (remember her?) catapulted ahead as a result of the horrendously over-hyped Ames straw poll. All of these twists and turns are captured in “Caucus,” Schnack’s funny, absorbing and improbably moving chronicle of a campaign that featured more than its share of characters, from Newt “He’s Baaack” Gingrich to Herman Cain, who in the movie proves he has considerable crooning chops.

Viewers expecting a fish-in-a-barrel hit job from “Caucus” (which screened at AFI Docs in 2013) should manage their expectations: While Schnack is ever-alert to amusing moments – many of them by way of Bachmann’s hilariously loose cannon of a husband, Marcus – he’s never condescending or snide. He’s made a film that both celebrates the folksy idiosyncrasies of retail politics and wistfully demonstrates the system’s costs. While candidates surge and recede (with Mitt Romney deigning to show up once or twice while his fellow candidates shamelessly race to the next pork tenderloin sandwich joint), the stalwart, tortoise-like Rick Santorum emerges as the film’s protagonist, his quiet focus and sincerity speaking volumes above the chatter and obfuscation that seemed to escalate with every photo opp.

It’s during Santorum’s encounters with older, white disaffected Iowans that the fear and anger that seem to animate so much of conservative politics come into stinging but also sad relief: To his enormous credit, the former Pennsylvania senator never hesitated to challenge an interlocutor on their statistics or assumptions, even if he did so with almost pastoral gentleness.

As Santorum wearily makes his way through all 99 Iowa counties – a doggedness that would be rewarded at the January caucuses – it’s possible to see the energy he derives from such exchanges, but also the deep toll. Regardless of whether you agree with Santorum’s policies or not, he emerges as a genuine, authentic figure – a tribute to Schnack’s own filmmaking, here blessedly pressed into service on behalf of light rather than heat. It’s not unlikely that Santorum will decide to run again in 2016, making “Caucus” not just delightful watching, but required viewing.

“Caucus” (104 minutes, on iTunes, Amazon Instant Video and Movies on Demand) is not rated. It contains nothing objectionable.

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Comments our editors find particularly useful or relevant are displayed in Top Comments, as are comments by users with these badges: . Replies to those posts appear here, as well as posts by staff writers.